1. Field of the Invention
This invention relates to reading magnetic images with the application of a variable mechanical pressure between the media being read and the read head, and, more particularly to using such variable pressure for reading bank information recorded on a check using magnetically readable ink.
2. Description of the Related Art
The capability for reading the account information printed on checks by means of magnetic inks is increasingly being provided in point-of-sale terminals. This information typically describes the bank to which the check is to be directed and the particular account number and check number of the check. This information is read with a magnetic read head to drive an electronic character recognition using a method generally called MICR (Magnetic Ink Character Recognition), with the recognized codes being transmitted for comparison within a data bank to determine if the check presented at a point of sale, and then inserted within the terminal, is from a supply of checks upon which one or more bad checks has been written or if the check is from a supply of checks which has been reported as stolen.
The capability for reading magnetic ink characters on a check is often included within a point-of-sale printing terminal for printing franking information on the check, and/or for printing customer receipts and journal information. The franking information endorses the check so that it is ready for deposit into an account of the retailer. For example, U.S. Pat. Nos. 5,634,729 and 5,865,547 describe printers having this capability, each of which also includes magnetic read head for reading the magnetically encoded printed characters on a check. When franking information is printed on the check, both printing and character recognition occur as a check is passed once through the terminal.
A problem with this type of operation arises from the frequency of times when magnetic ink characters are misread, particularly because printed check forms become wrinkled, worn, or otherwise damaged during handling. When this problem occurs, the character recognition program provides an indication that a legitimate character has not been read, so that the cashier can visually read the account information, which is supplied to the system by means of a 10-key keypad forming a part of a cash register system or another device associated with the terminal. Since this problem often occurs when a line of people are waiting for the cashier, the time required for keying the data is a potential inconvenience. While U.S. Pat. No. 5,634,729 describes performing repeated attempts to read the information, until it has been correctly read, the conditions under which the additional attempts are made are the same as the conditions of the original attempt. Thus, these additional attempts often produce the same result, without correcting the information. What is needed is a mechanism for improving the accuracy of character recognition by changing the conditions under which repeated attempts are made to read the information.
Magnetically encoded information, whether in the form of magnetic structures recorded within a magnetic medium, such as a magnetic tape, or in the form of characters printed on a nonmagnetic medium using magnetic ink, is typically read using a magnetic read head on a front side of the medium and a back-up plate on the rear side of the medium to hold the medium against the magnetic head.
A number of examples from the patent literature describe apparatus for adjusting and maintaining a predetermined level of force through the medium to a magnetic read head. For example, U.S. Pat. No. 3,157,868 describes a pressure pad for use with a magnetic head, past which a number of spaced, noncontinuous documents having magnetically encoded information are passed. The pressure pad is formed by the peripheral surface of a roller in a xe2x80x9cVxe2x80x9d-shaped groove in a block which is spring biased toward the read head. When the medium is first moved between the roller and the read head, an impact loading associated with the passage of the leading edge of the medium causes the roller to turn through a small distance; then friction between the xe2x80x9cVxe2x80x9d-shaped groove and the roller overcomes friction between the roller and the medium, so that the roller is held stationary. In this way, a new surface of the roller is presented to contact the medium, minimizing wear of the roller. Also, U.S. Pat. No. 4,638,392 describes the adjustment of a magnetic head to a spring-biased mounting plate by means of three or four screws extending around the magnetic head.
U.S. Pat. No. 5,602,688 describes a method and apparatus for controlling surface pressure exerted on a movable magnetic head, such as the rotating magnetic head of a video recorder, by a recording medium, such as a videotape, to provide optimum contact between the movable magnetic head and the recording medium with high precision in a wide frequency range. The estimated surface pressure exerted is compared to a reference surface pressure in order to develop a surface pressure control signal. The surface pressure tension of the magnetic recording medium and the position of the movable magnetic head may be controlled in accordance with the surface pressure control signal. While this method provides for maintaining the surface pressure exerted on the magnetic head at a predetermined level both in a normal and fast forward mode of playback or recording, there is no means for compensating for a poorly-recorded or damaged tape by varying the surface pressure. Still, what is needed is a method to make such compensation, together with a method for making repeated attempts at reading data at such a compensation method is applied.
The patent literature also describes the movement of backup rollers to select among a number of magnetic heads which are available for use. For example, British Patent 926,010 describes a head assembly in which a number of cams is used to move a similar number of spring biased backup rollers into and out of contact with a film medium adjacent a similar number of magnetic heads for reading and/or recording of data. This head assembly is used, for example, with both 35-mm and 70-mm film having magnetic tracks for information recording. The spring rollers are brought into contact only at those head positions which are compatible with the particular type of film being used. The cams are mounted on a shaft which is manually turned with a knob.
It is therefore an objective of the present invention to improve the accuracy of reading magnetically encoded information on a document by causing the information to be read up to a predetermined maximum number of times, with the pressure established between the document and a magnetic read head being increased between each reading of the information.
It is another objective of the present invention to provide a process in which repeated readings of information are stopped when it is determined that errors are not present within the information as read.
According to a first aspect of the present invention, apparatus is provided for reading magnetically encoded information on a document, with the apparatus including a document path along which the document is moved, a magnetic read head adjacent to a first side of the document path, a pressure plate adjacent a second side of the document path, opposite the first side, a pressure application mechanism, and a controller. The magnetic read head is aligned with the document path so that the magnetically encoded information moves adjacent to the magnetic read head as the document is moved along the document path with the magnetic information adjacent to the first side of the document path. The pressure plate is aligned with the magnetic read head so that the document moves along the document path between the pressure plate and the magnetic read head. The pressure application mechanism applies a level of pressure through the document between the pressure plate and the magnetic read head, with this level of pressure being varied in increments. The controller includes an error detection circuit or subroutine for determining when all codes within the magnetically encoded information have been correctly read. The controller also includes pressure control circuits for operating the pressure application means in response to the error detection circuits to increase the level of pressure following a failure to read all the codes correctly and before an additional attempt is made to read all of the codes correctly.